| Selective catalytic reduction Location 2 Location 1 Retractable lance


Benefits of Direct Injection SCR In addition to 11 fully tested and installed Direct Injection SCRs, EnergyLink is currently manufacturing 46 DI units and engineering another 86. These DI units will be used to control emissions from various turbines in both stationary and trailer-mounted power applications. Additionally, EnergyLink continues to design and supply conventional SCRs according to client preferences. However, most power developers are choosing Direct Injection for the


QUADRANT LABELS


View: side view looking south from north


View: looking upstream at turbine exit


Figure 6. Graphic representation of the Direct Injection duct with retractable lances and nozzles (not a final design). Source: EnergyLink International


Table 2. Test results: conventional SCR compared to Direct Injection SCR systems at full load for LM6000 and LM2500 gas turbines


LM6000 test rig - conventional AIG-AVS


Turbine load (full)


Ammonia distribution (%RMS) in ppmvdc


Stack exit NOX (mg/Nm3


in parentheses)


Ammonia slip in ppmvdc (mg/Nm3


in parentheses) 47 MW 5.80% 2.1 (1.46) 1.9 (1.32)


LM6000 test rig – Direct Injection


47 MW 5.30% 2.0 (1.39) 1.9 (1.32)


LM2500 actual – Direct Injection


25 MW 5.80% 2.0 (1.39) 2.3 (1.60)


Source: Environex, Inc, measurements carried out on Direct Ammonia Injection for EnergyLink International in 2022 and 2026. Note. The critical environmental criteria were 2.5 ppmvdc (4.7 mg/Nm3


) NOX at the exhaust stack exit and 10.0 ppmvdc (18.82 mg/Nm3


improves ammonia distribution by roughly 9% (5.3%RMS versus 5.8%RMS) compared with a conventional SCR system. For the LM2500, ammonia distribution matched the conventional SCR system’s root-mean-square percentage (%RMS) for ammonia distribution at 5.8%, while achieving 2.0 ppmvdc NOx


at the stack exit and


an ammonia slip of 2.3 ppmvdc, both emissions below the 2.5 ppmvdc NOx


and 10.0 ppmvdc NH3 limits. All other toxins in the LM2500 units’


Figure 7. LM2500 in Texas with Direct Injection SCR installed. Image: EnergyLink International


) ammonia slip


gas stream were reduced to permitted limits: CO removal reached 95% with levels below 1.0 ppmvcd for VOCs, 20 ppmvdc for formaldehyde, and under the detectable range at the turbine exit for acrolein.*


Meeting the regulatory limits for the field- installed units confirmed the effectiveness of EnergyLink’s Direct Injection technology.


following reasons: ● Equivalent to better NOx


/CO compliance.


EnergyLink continues to enhance the performance of its Direct Injection system. First, fine-tuning the number and position of the Direct Injection lances and nozzles optimises ammonia flow and improves the ammonia-to-NOx


balance, performing as well


as, or better than, a conventional SCR, even with higher-exhaust-temperature turbines, such as the LM2500XPRESS and SGT800. The higher-temperature exhaust streams, at or above 537°C (1000°F), must be cooled or tempered with air from blowers to an optimum catalyst temperature, in the range 454–482°C (850–900°F). Direct Injection systems easily accommodate tempering air systems.


● Reduced footprint. A conventional SCR catalyst requires a large surface area to effectively slow down the turbine exhaust so that NOx


can react with the ammonia reagent. In a traditional SCR, the ammonia injection grid must be similarly sized, with very fine nozzle spacing, to distribute ammonia evenly over the catalyst. EnergyLink’s DI system shortens the overall length of the SCR by creating a more even mix of ammonia with the exhaust gases at the turbine outlet. This eliminates the AIG section of a traditional SCR system, creating a smaller footprint (see Figure 8), which is important when plant real estate is scarce, when SCRs need to be shoehorned into existing facilities, or when fitting the SCR onto a trailer.


● Reduced costs. Direct Injection eliminates the Ammonia Injection Grid (AIG), the Ammonia Vaporiser Skid (AVS), and related heaters (see Figures 9, 10 and 11). While traditional SCRs can now also use multi- emission catalysts instead of separate CO and SCR catalysts, EnergyLink’s Direct Injection SCR was specifically designed to support the new multi-function catalyst, further reducing the SCR’s size. Simplifying an SCR by removing components and shrinking its size significantly lowers capital, installation, maintenance, and operating costs. For example, relocating ammonia injection from its upstream position in a conventional SCR to the turbine outlet in a Direct Injection unit eliminated over three tons of stainless steel and 650 feet of piping. The smaller size and fewer components also save on shipping and installation, requiring fewer and smaller trucks to transport the SCRs and smaller crews to install the units on site. The


* Environex, Inc (March 2026), LM2500 emissions measurements for EnergyLink International


www.modernpowersystems.com | May/June 2026 | 21


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